Converting from Device Names to UUIDs for Encrypted Devices

When configuring a Navigator Encrypt mount point, you can use either the device name (sample device name: /dev/sdb1) or the UUID (sample UUID: 3a602a15-11f7-46ac-ae98-0a51e1b25cf9) to configure the mount point. For more information, see Navigator Encrypt and Device UUIDs.

The UUID mount point configuration choice is preferable for Navigator Encrypt, because the device name can change when the system is rebooted or new  disks are added, but the UUID never changes. You can only use the UUID (--use-uuid) configuration option during the initial mount point configuration. You cannot use the UUID mount point configuration option on existing mount points that were created in Navigator Encrypt 3.12.0 or earlier, or that were configured to use the device name instead of the UUID.

For configurations where a device name was used, and you wish to convert to a UUID, you have the option to use the UUID conversion utility (navencrypt-prepare --convert-uuid), which converts existing mount points from using the device name to using the UUID. The UUID conversion utility updates the Navigator Encrypt configuration files to use UUIDs, and then reloads the updated mount points. You can perform this conversion on mount points with encrypted data without any impact on that data.

Preparing for UUID Conversion

The UUID conversion utility runs as part of the navencrypt-prepare command:

# navencrypt-prepare -h
...
--convert-uuid --all|--device=DEVICE
    Converts devices that are stored using the device name to instead use its uuid.
    '--all' will attempt to convert all device names in the navencrypt ztab file.
    '--device=DEVICE' will convert a single device.
...

As shown, you have two options when running the UUID conversion utility:

--device=DEVICE
Use this option to run the conversion against a single specified device.
--all
Use this option to run the conversion against all mount points that are currently using the device name instead of the UUID as defined in the /etc/navencrypt/ztab file.

The conversion utility first backs up all files in /etc/navencrypt to a timestamped directory under /tmp. Ensure that the user running the navencrypt-prepare operation has permission to write to /tmp. If this backup directory is not created, then the conversion script will exit without making any changes to the Navigator Encrypt configuration files.

Converting a Single Device

Use the UUID conversion utility --device=DEVICE option  to convert from a device name to UUID for a mount point on a single  device. It is recommended that you test the conversion against at least one device before running it  against all devices:

# navencrypt-prepare --convert-uuid --device=/dev/xvdd 
Backing up /etc/navencrypt to /tmp/navencrypt_bkup_20180917_135716 ... 
Stopping navencrypt-mount... 
Stopping navencrypt directories

Umounting /dev/xvdd ... [ OK ]
Umounting /dev/xvde ... [ OK ]
Umounting /dev/xvdf ... [ OK ]
* Unloading module ... [ OK ] 
Running conversion on /dev/xvdd
... ..

You must approve and finalize the conversion before it is complete.

Converting All Available Devices

Use the UUID conversion utility --all option to convert from the device name to the device UUID on all available devices. The conversion utility skips loop devices because they do not  have a dedicated UUID:

# navencrypt-prepare --convert-uuid --all 
Backing up /etc/navencrypt to /tmp/navencrypt_bkup_20180917_135731 ... 
Stopping navencrypt-mount... 
Stopping navencrypt directories
* Umounting /dev/xvdd ...                                 [  OK  ]
* Umounting /dev/xvde ...                                 [  OK  ]
* Umounting /dev/xvdf ...                                 [  OK  ]
* Unloading module ...                                    [  OK  ] 
Running conversion on /dev/xvdd... 
Running conversion on /dev/xvde... 
Running conversion on /dev/xvdf... ...

You must approve and  finalize the conversion before it is complete.

Finalizing the Conversion

Before the device name-to-UUID conversion is applied to the  configuration files, you must review and approve the differences between the  /etc/navencrypt/ztab and  /etc/navencrypt/control by either  accepting the changes ("y"), or rejecting them ("n").

# navencrypt-prepare --convert-uuid --all
...
Running conversion on /dev/xvdd...
Running conversion on /dev/xvde...
Running conversion on /dev/xvdf...

Showing diff of ztab and control files

---------------------------------------------
                    ZTAB
---------------------------------------------
2,4c2,4
< /navencrypt_mount/block1     /dev/xvdd     luks     key=keytrustee
< /navencrypt_mount/block2     /dev/xvde     luks     key=keytrustee
< /navencrypt_mount/block3     /dev/xvdf     luks     key=keytrustee
---
/navencrypt_mount/block1       /dev/disk/by-uuid/4206d6d5-6014-435a-b342-1d3dad5559a2     luks     key=keytrustee
> /navencrypt_mount/block2     /dev/disk/by-uuid/b84c4f38-bc74-40bc-87eb-2e857a996933     luks     key=keytrustee
> /navencrypt_mount/block3     /dev/disk/by-uuid/622312d0-0e6c-4e37-adeb-f6066a1df07d     luks     key=keytrustee
---------------------------------------------
                  CONTROL
---------------------------------------------
8c8
<     "name":     "/dev/xvdd",
---
>     "name":     "/dev/disk/by-uuid/4206d6d5-6014-435a-b342-1d3dad5559a2",
11c11
<     "name":     "/dev/xvde",
---
>     "name":     "/dev/disk/by-uuid/b84c4f38-bc74-40bc-87eb-2e857a996933",
14c14
<     "name":     "/dev/xvdf",
---
>     "name":     "/dev/disk/by-uuid/622312d0-0e6c-4e37-adeb-f6066a1df07d",


Accept changes? [y/N] y
Moving KeyTrustee deposit for /dev/xvdd...
Moving KeyTrustee deposit for /dev/xvde...
Moving KeyTrustee deposit for /dev/xvdf...
Operation complete
Overwriting old files...
Starting navencrypt-mount...
Starting navencrypt directories
 * Mounting '4206d6d5-6014-435a-b342-1d3dad5559a2'         [  OK  ]
 * Mounting 'b84c4f38-bc74-40bc-87eb-2e857a996933'         [  OK  ]
 * Mounting '622312d0-0e6c-4e37-adeb-f6066a1df07d'         [  OK  ]

If you reject the changes, the updated files are saved to /etc/navencrypt/ztab.new and /etc/navencrypt/control.new, and the existing ztab and control files remain unchanged.

# navencrypt-prepare --convert-uuid --all
...
Accept changes? [y/N] n

Changes will not be applied. Proposed changes are saved to /etc/navencrypt/ztab.new and /etc/navencrypt/control.new

Rolling Back the UUID Conversion

If you experience any problems with the device name-to-UUID conversion, you can restore the previous mount point state by replacing the contents of the /etc/navencrypt/directory with the backup created by the conversion utility:

# service navencrypt-mount stop
# rm /etc/navencrypt/keytrustee/deposits/dev.disk.by-uuid.*
# cp -rp /tmp/navencrypt_bkup_date_time/* /etc/navencrypt/
# service navencrypt-mount start